Optimizing the thermal effectiveness of an insulation wrap with internal folded polypropylene film for the transportation of frozen food

• A new type of insulation with an internal folded film is presented.
• A mathematical model of heat transfer was constructed.
• The theoretical model was experimentally validated.
• Recommendations are made for the arrangement of the internal folds.

The paper presents an investigation of the thermal performance of an innovative insulation wrap for food freezing, transportation and storage. The wrap is made of two outer polypropylene films and an internal folded polypropylene film welded together to form rectangular internal air cells. A mathematical model of heat transfer is presented and experimentally validated, with discrepancies less than 10% when there is no internal convection effect and generally less than 12% when internal convection is present. A thermal effectiveness of film usage was proposed and analyzed in order to find the best fold geometry. A mathematical model of the effectiveness and its experimental validation showed good agreement (discrepancies less than 13%). By using a criteria map, we recommend the following geometry: wrap thickness more than 5 and less than 10 mm; fold spacing more than 6 and less than 10 mm.